Tank holder



FIG. 1 is a front elevational view of a tank holder showing my new design;

FIG. 2 is a rear elevational view thereof;

FIG. 3 is a side elevational view thereof, the opposite side being a mirror image;

FIG. 4 is a top plan view thereof, the bottom plan being a mirror image. 

The ornamental design for a tank holder, as shown and described. 